Integrated transceiver with lightpipe coupler

ABSTRACT

Systems and methods for configuring an integrated transceiver are disclosed. In one embodiment, very small form factor transceivers can be configured to allow 10 G optical interconnects over distances up to 2 km. Transceiver circuitry can be integrated on a single die, and be electrically connected to a transmitter such as a laser-diode and a receiver such as a photo-diode. In one embodiment, the laser and photo diodes can be edge-operating, and be mounted on the die. In one embodiment, one or both of the diodes can be surface-operating so as to allow relaxation of alignment requirement. In one embodiment, one or both of the diodes can be mounted on a submount that is separate from the die so as to facilitate separate assembly and testing. In one embodiment, the diodes can be optically coupled to a ferrule via an optical coupling element so as to manage loss in certain situations.

RELATED APPLICATIONS

This application claims priority benefit of U.S. Provisional PatentApplication No. 60/750,488 filed Dec. 14, 2005, titled “Novel Low-costTransceiver Approach,” which is incorporated herein by reference in itsentirety.

This application relates to U.S. patent application Ser. No. 11/611,042,titled “INTEGRATED TRANSCEIVER USING EDGE DETECTING PHOTODETECTOR,” U.S.patent application Ser. No. 11/611,065, titled “INTEGRATED TRANSCEIVERUSING SURFACE DETECTING PHOTODETECTOR,” and U.S. patent application Ser.No. 11/611,093, titled “INTEGRATED TRANSCEIVER USING SUBMOUNT,” eachfiled on even date herewith.

BACKGROUND

1. Field

The present disclosure generally relates to optoelectronic devices, andmore particularly, to integrated transceivers having emitter anddetector incorporated therewith.

2. Description of the Related Art

A transceiver is a device that has both a transmitter and a receiver.Typically, the transmitter and receiver share at least some commoncircuitry, and sometimes, the same housing.

An optical transceiver is a device that receives and transmits opticalsignals. The transmitter in the optical transceiver is typically adevice such as a laser that modulates light outputs based on electricalinput signals. The receiver in the optical transceiver is typically adevice such as a photo-detector that converts optical input signals intoelectrical output signals.

Optical transceivers are commonly used in digital data communicationapplications, such as telecommunication. What is needed are opticaltransceivers that are fast, provide high bandwidth, and have reducedform factor.

SUMMARY

A wide variety of systems, devices, methods, and processes comprisingembodiments of the invention are described herein. Systems and methodsfor configuring an integrated transceiver can include, in one embodimentamong others, a very small form factor transceiver that can beconfigured to allow 10 G optical interconnects over distances up to 2km. In one embodiment, transceiver circuitry can be integrated on asingle die, and be electrically connected to a transmitter such as alaser-diode and a receiver such as a photo-diode. In one embodiment, thelaser and photodiodes can be edge-operating, and be mounted on the die.In one embodiment, one or both of the diodes can be surface-operating soas to allow relaxation of alignment requirement. In one embodiment, oneor both of the diodes can be mounted on a submount that is separate fromthe die so as to facilitate separate assembly and testing. In oneembodiment, the diodes can be optically coupled to a ferrule via anoptical coupling element so as to manage loss in certain situations.

For example, one embodiment of the present disclosure relates to anintegrated transceiver that includes a die including a plurality ofsemiconductor electronic devices. The integrated transceiver furtherincludes an edge detecting photodetector and a semiconductor laser suchas an edge emitting semiconductor laser. The plurality of semiconductorelectronic devices are electrically coupled to the photodetector and thelaser to process optical input received by the photodetector and controloptical output produced by the laser. The photodetector may beintegrated in the die and may be optically coupled to the fiber via awaveguide and a grating coupler. In this manner, light may be coupledvertically into and out of the surface of the die. The die may comprisea complementary metal oxide semiconductor (CMOS) die, for example, whichenables the integration of optical, optoelectronic, and electronicdevices on the die.

Another embodiment of the present disclosure relates to an integratedtransceiver that includes a die having semiconductor electronics. Theintegrated transceiver further includes a photodetector mounted on thedie. The integrated transceiver further includes a laser also mounted onthe die, with the semiconductor electronics electrically coupled to thephotodetector and the laser to process optical input received by thephotodetector and control optical output produced by the laser. Theelectronic die, the photodetector, and the laser form an integral unithaving a largest dimension that is less than approximately 10 mm×9 mm×4mm.

Yet another embodiment of the present disclosure relates to anintegrated transceiver that includes a die having top and bottomsurfaces, with the die including a plurality of semiconductor electronicdevices thereon. The integrated transceiver further includes asemiconductor laser mounted to the die, with the laser electricallycoupled to at least one of the semiconductor electronic devices on thedie to drive the laser. The integrated transceiver further includes aphotodetector electrically coupled to at least one of the semiconductorelectronic devices on the die to process optical input received by thephotodetector. The semiconductor photodetector includes a semiconductorregion having an optical input surface for receiving light, with theoptical input surface being oriented at an angle with respect to the topsurface of the die.

Yet another embodiment of the present disclosure relates to anintegrated transceiver that includes at least one die including aplurality of semiconductor electronic devices thereon. The integratedtransceiver further includes a semiconductor laser having an opticaloutput region configured to output laser light. The integratedtransceiver further includes a photodetector having an optical inputregion including an input surface configured to receive light to bedetected. The photodetector and the semiconductor laser are electricallycoupled to the semiconductor electronic devices, and the optical inputregion of the photodetector and the optical output region of the laserare directed in substantially the same direction and separated by adistance of less than about 1000 microns.

Yet another embodiment of the present disclosure relates to anintegrated transceiver that includes at least one die includingelectronics thereon. The integrated transceiver further includes asemiconductor laser having an optical output region configured to outputlaser light, with the laser in electrical communication with theelectronics. The integrated transceiver further includes a photodetectorhaving an optical input region configured to receive light to bedetected, with the photodetector in electrical communication with theelectronics. The integrated transceiver further includes a supportassembly on which the semiconductor laser and the photodetector aremounted such that the optical output region of the laser and the opticalinput region of the photodetector are separated by a distance of lessthan about 1000 microns.

Yet another embodiment of the present disclosure relates to anintegrated transceiver that includes at least one die includingelectronics thereon. The integrated transceiver further includes asemiconductor laser disposed on the at least one die and in electricalcommunication with the electronics. The integrated transceiver furtherincludes a photodetector disposed on the at least one die and inelectrical communication with the electronics. The integratedtransceiver further includes a light pipe having a length ofsubstantially optically transmissive material having a first end and asecond end, with the second end disposed proximal to the photodetector,the second end having a sloping reflective surface angled such thatlight propagating along the length from the first end to the second endis redirected to the photodetector.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of one embodiment of an integratedtransceiver that includes a die, a photo-detector such as a photo-diode,and an emitter such as a laser-diode;

FIG. 2 shows that in one embodiment, the integrated transceiver of FIG.1 can have a very small form factor (VSSF);

FIG. 3 shows a perspective view of one embodiment of the integratedtransceiver of FIG. 1;

FIGS. 4A-4C show different views of one embodiment of the integratedtransceiver, where the photo-diode and the laser-diode can be configuredfor edge-detecting and edge-emitting of signals, respectively;

FIGS. 5A and 5B show different views of one embodiment of a packagedassembly having the die-mounted edge-detecting/emitting diodes so as tofacilitate optical coupling with a coupler such as a multi-fiberassembly;

FIGS. 6A-6D show different views of one embodiment of the integratedtransceiver, where the photo-diode can be configured forsurface-detection of signals;

FIG. 7A shows one embodiment of a package configured to allow mountingof a die and a surface-detecting photo-diode;

FIGS. 7B and 7C show different view's of the package of FIG. 7A with thedie and the surface-detecting photo-diode mounted so as to facilitateoptical coupling with the multi-fiber assembly;

FIGS. 8A and 8B show example geometric design considerations forplacement of various components of the integrated transceiver;

FIGS. 9A-9D shows different views of one embodiment of the integratedtransceiver, where the photo-diode and the laser-diode can be mounted ona submount and electrically coupled to the die;

FIG. 10 shows a more detailed view of one embodiment of the submount;

FIGS. 11A-11C show different views of one embodiment of the integratedtransceiver, where the surface-detecting photo-diode can be opticallycoupled with the multi-fiber assembly via an optical coupling element;

FIGS. 12A-12C show different views of one embodiment of the integratedtransceiver, where the surface-detecting photo-diode and thesurface-emitting laser-diode can be coupled with the multi-fiberassembly via the optical coupling element;

FIGS. 13A-13C show different views of one embodiment of the integratedtransceiver, where the emitter and the detector can be integrated into asingle chip and be coupled with the multi-fiber assembly via the opticalcoupling element; and

FIGS. 14A and 14B show examples of some design considerations for theexample edge-detecting photo-diode.

These and other aspects, advantages, and novel features of the presentteachings will become apparent upon reading the following detaileddescription and upon reference to the accompanying drawings. In thedrawings, similar elements have similar reference numerals.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

Certain embodiments of the present disclosure relate to integratedtransceivers. In some embodiments, such transceivers can have small formfactors (SFF) or very small form factors (VSFF).

In some embodiments, the SFF or VSFF integrated transceivers can bepackaged in a relatively low cost manner and enable 10 G opticalinterconnects over distances up to 2 km. Such economical packaging canlead to proliferation of 10 G interconnects, and can lead to fasteroptical interconnects with data rates of 100 G (Gb/s) and higher.

In designing such integrated transceivers, cost can be an importantfactor. Cost associated with the integrated transceivers can include,for example, component costs, cable and connectorization costs,footprint, and cooling cost. In some embodiments, such design costs canbe addressed by packaging the integrated transceiver in a VSFFconfiguration.

For example, the transceiver's size can be reduced (thus reducing thefootprint) significantly by integrating various functionalities of thetransceiver on one or more dies. In a typical transceiver, a PCB(printed circuit board) is usually the largest part; thus in oneembodiment, the electronic components associated with the PCB can beintegrated on a single die. In some embodiments, such integration ofelectrical components on a die can reduce electrical parasiticsassociated with various connections in the PCB, and thereby improve highspeed performance of the transceiver.

Typically, the second largest parts in a transceiver are transmitteroptical sub-assembly (TOSA) and receiver optical sub-assembly (ROSA).Thus in one embodiment, various functionalities of TOSA and ROSA can beconsolidated so as to reduce the size of the transmitter.

In one embodiment, the transceiver can also be made to be less expensiveby consolidating all or substantially all of the electronic componentson a single die. Such integration can reduce the number of opticalalignments. Moreover, integration of the various components can providefeatures such as elimination of at least two laser welding steps (onefor ROSA and one for TOSA), elimination of a need for pigtailed devices,and/or improved heat sinking of laser and die.

FIG. 1 shows a block diagram of one embodiment of an integratedtransceiver 100 that includes a die 102, an emitter 104 such as alaser-diode, and a photo-detector 106 such as a photo-diode. In oneembodiment, the integrated transceiver 100 can have a single die. In oneembodiment, the integrated transceiver 100 can have two dies. In oneembodiment, the integrated transceiver 100 can have more than two dies.

As further shown in FIG. 1, the integrated transceiver 100 can beconfigured to facilitate optical coupling with a coupler 108. In oneembodiment, the coupler 108 can be a multi-fiber assembly. In oneembodiment, the multi-fiber assembly can include an assembly that holdstwo or more fibers. In one embodiment, the multi-fiber assembly caninclude injection molded plastic with holes dimensioned to hold fiberends or stubs. In one embodiment, the multi-fiber assembly can be adevice that conforms to an industry standard. For example, themulti-fiber assembly can be any one of mini-MT or MT type connectors.

FIG. 2 shows that in one embodiment, the integrated transceiver 100 ofFIG. 1 can be a configured to be a VSFF transceiver 110. Accordingly, adie 112, a laser-diode 114, and a photo-diode 116 can be configured toconform to the VSFF configuration, and to allow optical coupling with aferrule 118.

FIG. 3 shows a perspective view of one embodiment of an integratedtransceiver assembly 120 having a die 122 mounted to a packagingsubstrate 130. In one embodiment, the substrate 130 can be formed fromceramic. In one embodiment, the substrate 130 can be dimensioned tofacilitate positioning of a ferrule 140. The ferrule 140 can includeinput and output optical fibers 144 that terminate at a housing so as toallow optical coupling with transmitter and/or receiver components.

As further shown in FIG. 3, the integrated transceiver assembly 120 alsoincludes transmitter and receiver components (124 and 126) that can bemounted to or about the die 122. Various transceiver and receiverplacement configurations are described below in greater detail.

In some embodiments, the die can include a plurality of semiconductorelectronic devices. In one embodiment, such semiconductor electronicdevices can include a laser driver and a transimpedance amplifier tofacilitate operation of laser and photodiode. In one embodiment, the dieincludes a semiconductor (for example, silicon) substrate or a substratehaving semiconductor disposed thereon.

In one embodiment, the die can have top and bottom surfaces, and aplurality of sides thereabout. The die can be mounted on a packagingsubstrate (such as the substrate 130 in FIG. 3) so that the bottomsurface of the die is mounted to the packaging substrate, eitherdirectly or via one or more intervening layers. The top surface of thedie can be configured to allow mounting of the laser and/or photodiode,and/or connections for such diode.

In one embodiment, each of the plurality of sides can define an edge. Inone embodiment, such an edge can facilitate mounting and operation ofedge-emitter and/or edge-detector.

An edge detecting photodetector may for example comprise a multilayerstructure having a top and a bottom and side surfaces. The bottom of themultilayer structure may be disposed on the top surface of the die. Themultilayer structure may comprise a plurality of layers stacked on topof each other. In some embodiments, the layers form a planar waveguide.Light may be coupled into the side of the edge detecting photodiode. Inparticular, the waveguide has an input and is optically coupled to aphotosensitive region of the detector. Light is introduced into theoptical input of the optical waveguide and is guided to thephotosensitive region that converts the optical signal into anelectrical signal. One example of such a device is a commerciallyavailable 40 G edge detection photo-diode available from ArchcomTechnology, Inc., of Azusa, Calif. Other configurations are alsopossible. For example, light may be coupled into the top surface of dievia a grating coupler.

FIGS. 4A-4C show different views (top, side, and front views,respectively) of one embodiment of an integrated transceiver assembly150, where a laser-diode 154 and a photo-diode 156 can be configured toprovide at least one of edge-emitting and edge-detectingfunctionalities. Accordingly, at least one of the laser and photodiode154 and 156 can be mounted on the die 152 at or near one of the edges.

In one embodiment, the photo-diode 156 can be an edge-detecting type,and be mounted at or proximal to the edge of the die 152. In oneembodiment, both of the photo and laser diodes can be edge-operatingtype, and be mounted at or proximal to the edge of the die 152. In oneembodiment, each of the photo and laser diodes 154 and 156 arepositioned on the die 152 so that their active edges are within at leastabout 10 μm from the edge of the die 152. Other edge-positioningconfigurations are possible.

In one embodiment, the laser and photodiode 154 and 156 can be spaced ata selected distance so as to allow optical coupling with selected fiberends 176 of a ferrule assembly 170. Mini-MT multi-fiber assembly is anexample of such a ferrule assembly 170. In one embodiment, the ferruleassembly 170 can include a plurality of fiber ends that are opticallycoupled to input and output optical paths 174. In one such ferruleassembly, the fiber ends are spaced at approximately 250 μm. Thus, inthe example shown in FIG. 4A-4C, the laser and photo diode 154 and 156are spaced apart at about 750 μm. Other spacing configurations arepossible. For example, multiple laser diodes 154 and/or multiplephotodiodes may be included on the die as discussed below. Such laserdiodes 154 and/or photodiodes may be positioned to optically couple todifferent fibers in the ferrule.

In one embodiment, the edge-detecting photo-diode 156 includes amulti-layer structure having top, bottom, and side surfaces. The bottomsurface can be disposed on the top surface of the die 152, eitherdirectly or via one or more intervening layers. In one embodiment, ametal layer is disposed between the multi-layer structure of thephoto-diode 156 and the top surface of the die 152. In one embodiment,the multi-layer structure includes a waveguide that receives an opticalinput. The multi-layer also includes a photosensitive region thatconverts the optical input into an electrical signal. In certainembodiments the photosensitive region forms part of the waveguide.

In one embodiment, the edge-detecting photo-diode 156 can be a devicecomprising a III-V semiconductor material. As a non-limiting example,the edge-detecting photo-diode 156 may comprise an InGaAs type device.Such a device can be appropriate for use with, for example 1550 nmlight. One example of such a device is a commercially available 40 Gedge detection photo-diode available from Archcom Technology, Inc., ofAzusa, Calif. In one embodiment, the edge-detecting photo-diode 156 canbe a germanium device. In one embodiment, AlGaAs or Si basedphoto-diodes can also be used.

In one embodiment, the laser diode 154 can be an edge-emittingsemiconductor laser. An example of such semiconductor laser can includedevices having III-V semiconductor material. In one embodiment, thesemiconductor laser can be flip-chip bonded to the die.

In one embodiment, the foregoing example semiconductor laser 154 canhave an optical output region configured to output laser light. In oneembodiment, the above-described edge-detecting photo-diode 156 caninclude an optical input region configured to receive light to bedetected. In one embodiment, the optical output region of thelaser-diode 154 and the optical input region of the photo-diode 156 areseparated by a distance that is less than about 1,000 μm. Otherseparation configurations are possible.

In one embodiment, the optical output region of the laser-diode 154 andthe optical input region of the photo-diode 156 are within about 10 μmof being on the same plane above and parallel the upper surface of thedie 152. In one embodiment, the optical output region of the laser-diode154 and the optical input region of the photo-diode 156 aresubstantially coplanar. Other elevation configurations are possible.

In one embodiment, the separation and elevation configurations can be interms of distances with respect to geometric centers of the laser andphoto diodes. In one embodiment, such distances can be with respect toan intensity centroids associated with the diodes. Combinations of theabove two example conventions, as well as other conventions, arepossible.

In some embodiments, the optical axes of the fiber ends 176 can bepositioned so as to be substantially aligned with optical axes of thelaser-diode 154 and photo-diode 156. In the example configuration shownin FIG. 4B, the fiber ends 176 are depicted as being substantiallyaligned with the lower active surface of the laser-diode 154. If theactive surface was on the upper side of the diodes, or anywhere else onthe diodes, the fiber ends 176 can be positioned accordingly.

In one embodiment, at least some of the plurality of semiconductorelectronic devices of the die 152 can be electrically coupled to thelaser-diode 154 and the photo-diode 156, and be configured to controloptical output produced by the laser-diode 154 and process optical inputreceived by the photo-diode 156. In one embodiment, an assembly of sucha die 152, laser-diode 154, and photo-diode 156 has a dimension that isless than approximately 10 mm (length)×9 mm (width)×4 mm (thickness). Inone embodiment, the assembly of the die 152, laser-diode 154, andphoto-diode 156 form an integral unit having a largest dimension that isless than approximately 10 mm. Other dimensions are possible.

In one embodiment, as shown in FIGS. 4B and 4C, the die 152 can bemounted to the packaging substrate (for example, 130 in FIG. 3) via anadhesive layer 160. In one embodiment, the adhesive can be selectedbased on its thermal conductivity property. For example, an adhesivethat has a relatively good thermal conducting property can be selectedto reduce thermal resistance between the die 152 and the packagingsubstrate. Other attachment configurations are possible.

In one embodiment, various functionalities described in FIGS. 4A-4C canbe implemented in more than one die. In such a configuration, theplurality of die can be packaged on a multi-chip module (MCM) to providesubstantially similar functionalities.

In one embodiment, the integrated transceiver can be configured to havemore than one transmitter, and correspondingly more than one receiver.As shown in FIG. 4A, the ferrule assembly 170 can house more than twofiber ends 176. The example ferrule 170 is depicted as having four fiberends. Thus, the integrated transceiver 150 can have a second laser-diode(not shown) mounted on the die 152, and a second photo-diode (not shown)mounted on the die 152 so as to provide two-channel functionality.

In one embodiment, as described above, spacing between the fiber endscan be approximately 250 μm. Thus, the example four components (twolasers and two photo-diodes) can be arranged with approximately 250 μmspacing intervals, such that the two outer-most components are separatedby approximately 750 μm.

FIG. 5A shows a front sectional view of one embodiment of a packagededge-operating integrated transceiver 180. FIG. 5B shows a top view ofthe packaged transceiver 180. As shown, the packaged transceiver 180 canincludes a packaging substrate 190 that defines a first recess 194dimensioned to allow mounting of a die 182. The example die 182 is shownto have mounted on it an edge-emitting laser-diode 184 and anedge-detecting photo-diode 186. In one embodiment, the die 182,laser-diode 184, and photo-diode 186 assembly can be similar to thatdescribed above in reference to FIGS. 4A-4C.

In one embodiment, as shown in FIG. 5A, the packaging substrate 190 canalso define a second recess 192 that allows access to the mounted die182 (or access to the first recess for mounting the die 182), and/or toprovide protection of the die/laser/photo-diode assembly. As describedabove in reference to FIG. 3, the packaging substrate (130 in FIG. 3)does not necessarily need to have a recess for mounting of the die(122). Thus, it will be understood that any number of die/substratemounting configurations are possible.

In one embodiment, as shown in FIG. 5B, the packaging substrate 190 canalso be configured to allow mounting of a monitor photo-detector (MPD)188. The MPD 188 can be configured to monitor the output of the laser184.

In one embodiment, as shown in FIG. 5B, the packaging substrate 190 canbe dimensioned to allow positioning of a ferrule assembly 200. Suchdimensioning can include one or more recesses or features that allowpositioning of the fiber ends (not shown) at desired locations relativeto the optical output and input regions of the laser-diode 184 andphoto-diode 186.

FIGS. 6A-6D show various views (top, first side, second side, and frontviews, respectively) of one embodiment of a transceiver assembly 210,where at least one of the transmitter and receiver is asurface-operating device. For the purpose of description, a photo-diode216 is depicted as being a surface-detecting device and a laser-diode214 is depicted as an edge-emitting device. However, it will beunderstood that in one embodiment, the photo-diode can beedge-detecting, and the laser-diode can be surface-emitting.

In one embodiment, the edge-emitting laser-diode 214 can be mounted to adie 212, and the surface-detecting photo-diode 216 can be mounted to amounting sub-assembly 218. In one embodiment, the die 212 can include aplurality of semiconductor electronic devices. At least some of thosedevices can be electrically coupled to the laser-diode 214 mounted onthe die 212, and to the photo-diode 216 (wire lead coupling depicted as222); and be configured to control optical output produced by thelaser-diode 214 and process optical input received by the photo-diode216.

In one embodiment, the structure and configuration of the die 212 can besimilar to that described above in reference to FIGS. 4A-4C.

In one embodiment, the example laser-diode 214 can be configured andmounted to the die 212 in a manner similar to the laser-diode 154described above in reference to FIGS. 4A-4C.

In one embodiment, a photo-diode 216 that is mountable on the mountingsub-assembly 218 can be a standardized component. For example,photo-diode products from companies such as Kyocera can be mounted tothe sub-assembly 218. Similarly, laser-diode products from companiessuch as Kyocera can also be mounted to a sub-assembly.

In one embodiment, the some or all of the mounting sub-assembly 218 canbe formed from ceramic. The ceramic support structure can include one ormore pathways for facilitating electrical connections between thephoto-diode 216 and the die.

In one embodiment, a support structure (such as ceramic structure) thatsupports the die 212 can be the part of the same structure that supportsthe photo-detector 216. In another embodiment, the support structure forthe die 212 is not part of the structure that supports thephoto-detector 216. These two separate structures may or may not becoupled mechanically.

In one embodiment, the photo-detector 216 can be a semiconductorphoto-detector that includes a semiconductor region having an opticalinput surface 224 for receiving light. The optical input surface can beoriented at an angle with respect to the top surface of the die 212.

In one embodiment, the photo-detector 216 can include a plurality ofelectrical leads that extend away from the detecting surface (rearwardif the detecting surface faces front). The plurality of electrical leadscontact the semiconductor region through bonds on a rearward side of thesemiconductor region (on the side opposite to the fiber). The bonds andleads extending from the photo-detector may in some embodiments have athickness that would otherwise prevent the fiber from being broughtsufficiently close to the detecting surface of the photo-detector if thelead were on the front side of photodetector. Accordingly, the bonds maybe on the rear side of the photo-detector with the fiber on the frontside of the detector. In one embodiment, a packaging of thephoto-detector 216 can include an optically transmissive panel forwardof the semiconductor region that transmits light to the semiconductorregion. For example, the photodiode may comprise semiconductor having aphotosensitive detecting surface mounted downward onto a package with anoptically transmissive aperture that permits light to pass through thepackage to the photosensitive detector surface of the semiconductor. Theopposite side of the semiconductor may include the electrical leads toprovide access for the fiber.

In one embodiment, the semiconductor region of the photo-detector 216can be a semiconductor diode. In one embodiment, the optical inputsurface of the semiconductor region can be substantially planar. In oneembodiment, the optical input surface can be oriented substantiallyorthogonal to the top surface of the die.

In one embodiment, the laser 214 has an output face. The optical inputsurface of the photo-detector 216 and the output face of the laser 214are directed substantially in the same direction. In one embodiment, theoptical input surface of the semiconductor region of the photo-detector216 and the output face of the laser 214 are coplanar.

In one embodiment, the output face of the laser 214 and the opticalinput surface of the photo-detector 216 can be within about 1 to 6degrees, and within about 60 microns (μm) of being coplanar. In oneembodiment, the output face of the laser 214 and the optical inputsurface of the photo-detector 216 are tilted with respect to each otherby about 4 to 10 degrees. The photo-detector may be tilted, for example,to reduce light reflected back into the fiber.

In one embodiment, the laser and photo diodes 214 and 216 can be spacedat a selected distance so as to allow optical coupling with selectedfiber ends of a ferrule assembly 230. In one embodiment, the ferruleassembly 230, and the selected spacing between the diodes, can besimilar to the ferrule 170 described above in reference to FIGS. 4A-4C.For example, the output face of the laser 214 and the optical inputsurface of the photo-detector 216 can be laterally separated from eachother, as measured center-to-center, by about 750 microns for opticalinterconnection with the selected fibers in the ferrule 230. Indifferent embodiments, the center-to-center distance may be larger orsmaller than 750 microns. In certain embodiments, however, thecenter-to-center distance is less than 1000 microns. In one embodiment,the center-to-center distance may be less than 750 microns (for example,about 250 microns).

In one embodiment, an assembly of such a die 212, laser-diode 214, andphoto-diode 216 can have dimensions that are similar to the assemblydescribed above in reference to FIGS. 4A-4C. In one embodiment, theassembly of the die 212, laser-diode 214, and photo-diode 216 form anintegral unit having a largest dimension that is less than approximately15 mm. Other dimensions are possible.

In one embodiment, as shown in FIGS. 6B-6D, the die 212 can be mountedto the packaging substrate (for example, 130 in FIG. 3) via an adhesivelayer 220. Other attachment configurations are possible.

In one embodiment, various functionalities described in FIGS. 6A-6D canbe implemented in more than one die. In such a configuration, theplurality of dies can be packaged on a multi-chip module (MCM) toprovide substantially similar functionalities.

In one embodiment, use of the surface-operating component (such as thesurface-detecting photo-detector 216) can allow use of standard parts,as well as providing a more relaxed alignment requirement for thesurface-operating component. In one embodiment, however, such featurescan be offset by size limitations that can be imposed by thesurface-operating component. For example, use of certain standardsurface-detecting photo-detectors may limit the integrated transceiverto a single channel device if coupled to certain type of Mini-MTmulti-fiber assembly.

FIG. 7A shows a front sectional view of one embodiment of a packagingassembly 240 that can be dimensioned to receive an integratedtransceiver similar to that described above in reference to FIGS. 4A-4D.In one embodiment, a packaging substrate 242 can define a first recess244 dimensioned to receive a die (for example, the die 212 of FIGS.6A-6D). In one embodiment, the first recess 244 can be formed within asecond larger recess 250 that allows access to the first recess 244 formounting of the die, or for accessing the mounted die, and/or to provideprotection of the die. As described above in reference to FIG. 3, thepackaging substrate (130 in FIG. 3) does not necessarily need to have arecess for mounting of the die. Thus, it will be understood that anynumber of die/substrate mounting configurations are possible.

In one embodiment, as shown in FIG. 7A, the packaging substrate 242 candefine a receptacle opening 246 dimensioned to receive asurface-operating component (for example, the surface-detectingphoto-detector 216 of FIGS. 6A-6D). The packaging substrate 242 canfurther define one or more pathways 247 dimensioned to facilitaterouting of wires that electrically couple the die with thephoto-detector 216.

FIG. 7B shows a similar view as FIG. 7A, but with a die 252 and asurface-detecting photo-detector 256 mounted in their respectiveopenings (244 and 246). An edge-emitting laser 254 can be mounted on thedie 252 in a manner described above in reference to FIGS. 6A-6D.Moreover, the first recess 244 and the receptacle opening 246 can bepositioned relative to each other such that the laser 254 and thedetecting surface 258 of the photo-detector 256 can be positioned at adesired orientation (desired center-to-center spacing, for example).

In some embodiments, the packaging substrate 242 is a monolithicstructure to which the photo-detector 216 as well as the die 252 aremounted, with the laser 254 being mounted to the die 252. Otherconfigurations, however, are possible.

FIG. 7C shows a top view of the packaged assembly of FIG. 7B. In oneembodiment, the packaging substrate 242 can be dimensioned to allowpositioning of a ferrule assembly 260. Such dimensioning can include oneor more recesses or features that allow positioning of the fiber ends(not shown) at desired locations relative to the optical output andinput regions of the laser 254 and photo-detector 256.

In one embodiment, as shown in FIG. 7C, the packaging substrate 242 canalso be configured to allow mounting of a monitor photo-detector (MPD)248. The MPD 248 can be configured to monitor the output of the laser254.

FIGS. 8A and 8B show one embodiment of an integrated transceiver 270having a surface-detecting photo-detector, where certain geometricparameters can be considered. FIG. 8A shows a front view of thetransceiver 270, and FIG. 8B shows a top view.

In FIG. 8A, a die 272 is shown to be mounted on a packaging substrate280. In one embodiment, the substrate 280 can be formed from ceramicmaterial. In one embodiment, the die 272 can be mounted on the substrate280 via a die attach layer 286 such as an adhesive layer. Anedge-emitting laser 274 is shown to be mounted on the die 272. Asurface-detecting photo-detector 276 (having a detecting surface 278) isshown to be mounted to the packaging substrate 280 via a mountingsub-assembly 282. In one embodiment, the die 272, laser 274, andphoto-detector 276 can be similar to those described above in referenceto FIGS. 6 and 7.

In one embodiment, as shown in FIG. 8B, the photo-detector 276 can beelectrically interconnected with the die 272 via connection lines 284 band 284 c. These connection lines 284 b and 284 c extend through thesub-assembly 282 to which the photo-detector 282 is mounted as well asthrough the portion of the package substrate 280 to which thesub-assembly 282 is mounted. In this embodiment the package substrate280 is shaped to accommodate mounting of both the die 272 and thesub-assembly 282. In one embodiment, the laser 274 can be electricallyinterconnected with the die 272 via one or more connection lines 284 a.Other configurations however, are possible.

In one embodiment, the center of the laser 274 can be positioned at aselected distance from the lateral edge of the die 272 (arrow 290 b). Inone embodiment, the selected distance 290 b can be approximately 250 μm.The edge of the die 272 can be positioned at a selected distance fromthe edge of the mounting sub-assembly 282 (arrow 290 c). In oneembodiment, the selected distance 290 c can be approximately 150 μm. Thecenter of the detecting surface 278 of the photo-detector 276 can bepositioned at a selected distance from the lateral edge of the mountingsub-assembly 282 (arrow 290 d). In one embodiment, the selected distance290 d can be approximately 350 μm. Based on the foregoing exampleconfiguration, the distance from the center of the laser 274 and thecenter of the photo-detector 276 (arrow 290 e) can be approximately 750μm.

In one embodiment, the lateral width of the laser 274 (arrow 290 a) canbe approximately 250 μm, and the length (arrow 290 f) can beapproximately 750 μm.

As previously described, the example 750 μm spacing between the laserand the photo-detector can facilitate optical coupling with certainferrules, such as the Mini-MT multi-fiber assembly. It will beunderstood that other spacing configurations are also possible.Accordingly, the center-to-center distance may be larger or smaller than750 microns. In certain embodiments, however, the center-to-centerdistance is less than 1000 microns.

FIGS. 9A-9D show various views (top, first side, second side, and frontviews, respectively) of one embodiment 300, where both transmitter 304and receiver 306 are mounted on a submount 310. In one embodiment, thesubmount 310 can be a single structure dimensioned to allow mounting ofthe transmitter 304 and receiver 306. In one embodiment, the submount310 can be formed by first and second structures 314 and 316 that arejoined together. The first structure 314 can be dimensioned to allowmounting of the transmitter 304, and the second structure 316 can bedimensioned to allow mounting of the receiver 306.

In one embodiment, the laser 304 and the photo-detector 306 can beelectrically coupled to a die via a plurality of electricalinterconnects 312. The electrical interconnects can include, forexamples, pins, sockets, wires, traces, conductive pathways imbedded inridged insulating material, or any combination thereof. Suchinterconnects can be used to provide electrical connection in otherembodiments describe herein as well.

The submount assembly 310 can thus be populated with one or more lasersand one or more photo-detectors separate from die-mounting operations.For example, such populating of the submount assembly 310 can beperformed without being impacted by die attaching adhesive thicknessvariations. Because both the laser and the photo-diode are mounted onthe same assembly substantially free from such variations, the laser andphoto-diode can be more accurately placed relative to each other.

Moreover, the use of submount for both transmitter and receiver canallow for separate assembly and testing of the optical subassembly priorto connecting it to the die 302.

In one embodiment, such as the example shown in FIGS. 9A-9D, the laser304 can be an edge-emitting type, and the photo-detector 306 can be asurface-detecting type (with a detecting surface 308). The example laser304 and the photo-detector 306 can be similar in configuration andrelative orientation to those described above in reference to FIGS. 6and 8. For example, the surface detecting photo-detector 344 maycomprise a planar photosensitive surface shown in FIG. 9D that receivesthe light. In the embodiment shown, this planar photosensitive surfaceis orthogonal to the top surface of the die 302. Other combinations oflaser and photo-detector types mounted on the subassembly 310 arepossible. Moreover, the die 302 can be configured in a manner similar tothose described above.

In one embodiment, as shown in FIGS. 9B-9D, the die 302 can be mountedto a packaging substrate (not shown) via an attachment layer 330 such asan adhesive layer. Similarly, the subassembly 310 can be mounted to apackaging substrate (not shown) via an attachment layer 332 such as anadhesive layer. The packaging substrate for the die 302 may or may notbe part of the same structure as that for the subassembly 310. Thepackaging substrate may comprise ceramic in certain embodiments. Ceramicis a material that can provide desired thermal, electrical, andmechanical properties as a packaging substrate. In one embodiment, othermaterials having such properties can also be used as a packagingsubstrate.

The subassembly 310 is configured couple with ferrule assembly 320. Inparticular, optical fiber ends in the ferrule may be aligned with thetransmitter 304 and receiver 306 to provided optical coupling betweenthe fiber ends and the transmitter and receiver.

FIG. 10 shows a perspective view of one embodiment of a support assembly340 that can be the subassembly 310 described above in reference toFIGS. 9A-9D. As previously described, such implementation of a submountcan provide various flexibility in manufacturing and/or testingprocesses.

In one embodiment, the support assembly 340 can include mountingsubstrate 342 having surfaces for mounting of a laser 344 and aphoto-detector 346. The laser 344 is depicted as being an edge-emittingtype, and the photo-detector 344 a surface-detecting type (with adetecting surface 348). It will be understood, however, that othercombinations of laser and photo-detector are possible. In oneembodiment, the support assembly 340 can also be dimensioned tofacilitate mounting of a monitor photo-detector (not shown).

The support assembly 340 is also shown to have a plurality of contacts352 that facilitate electrical connection of the laser 344 and thephoto-detector 346 with the die (not shown).

In one embodiment, the laser 344 and the photo-detector 346 can bepositioned and oriented relative to each other in a manner similar tothose described above in reference to FIGS. 6-9. For example, thedistance between the centers of the laser 344 and the photo-diode 346(arrow 350 a) can be approximately 750 μm. In another example, thelength of the laser 344 (arrow 350 b) can be approximately 250 μm,similar to the example laser described above in reference to FIG. 8B.Other dimensions, however, are possible. For example, in differentembodiments, the center-to-center distance may be larger or smaller than750 microns. In certain embodiments, however, the center-to-centerdistance is less than 1000 microns.

In one embodiment, the support assembly 340 can be formed from ceramic.In one embodiment, the support assembly 340 can be a monolithicstructure that supports both of the laser and photodetector. In oneembodiment, the support assembly 340 can include separate first andsecond subassemblies, with the laser mounted to the first subassemblyand the photo-detector mounted to the second subassembly. In oneembodiment, the support assembly 340 can comprise insulating materialand include conductive pathways therethrough or thereon that provideelectrical connections from the laser and the photo-detector to theelectronics on the die (not shown). The conductive pathways can lead tothe electrical contact 352 to provide electrical connections with theelectronics on the die (not shown). In one embodiment, the supportassembly 340 is positioned relative to the die so as to butt up againstthe die. In some embodiments, the electrical contacts 352 mate withother contacts mounted on the die.

FIGS. 11-13 show various embodiments of optical coupling configurationsbetween an integrated transceiver and a ferrule. In one embodiment 360shown in FIGS. 11A-11C, an optical coupling element 370 is shown tocouple light between an integrated transceiver and a ferrule 380. In oneembodiment 390 shown in FIGS. 12A-12C, an optical coupling element 400is shown to couple light between another integrated transceiver and aferrule 410. In one embodiment 420 shown in FIGS. 13A-13C, an opticalcoupling element 430 is shown to couple light between another integratedtransceiver and a ferrule 440. For the purpose of description, it willbe assumed that the optical coupling elements 370, 400, and 430 aresimilar; and ferrules 380, 410, and 440 are similar. Moreover, the dies362, 392, and 422 can be configured similarly in manners described above(including mounting via their respective mounting layers 374, 404, and434). However, it will be understood that such similarities are notrequirements, and that they may be different.

In one embodiment, the optical coupling element can include a light pipeor conduit having a length 371, 401, 431 of substantially opticallytransmissive material (for example, glass or plastic). The light pipe orlight guide can have a first end and a second end, with the second endbeing disposed proximal to a photo-detector (366, 396, and 425). In someembodiments, this light pipe may guide light from the first end to thesecond end in part via total internal reflection at the sidewalls. Muchof the light may however propagate forward from the first end to thesecond end without reflecting from the sidewalls. The second end caninclude a sloping reflective surface 373, 403, 433 angled such thatlight propagating along the length from the first end to the second endis redirected to the photo-detector. In one embodiment, the slopingreflective surface 373, 403, 433 can be angled such that a difference,between the angle of the sloping reflective surface (373, 403, 433)relative to the length of the light pipe and the incident angle of lightwith respect to a normal to the sloping reflective surface, is betweenabout 4° and 12°. If the length of the light pipe is horizontal and thedetector faces upwards, such an angle (e.g., between about 4° and 12°)represents the incident angle on the detector. In one embodiment, thesloping reflective surface 373, 403, 433 can include a total internalreflection surface. The sidewalls, including the sloping sidewalls canbe planar in some embodiments, although the shape should not be sorestricted. The sidewalls and in particular the sloping reflectivesidewall can be polished in some embodiments to reduce scattering oflight undergoing total internal reflection. A reflective coating (e.g.,an interference coating or metallization) can be used in someembodiments. Examples of embodiments of optical coupling elements aredisclosed in U.S. application Ser. No. 11/109,210 titled “PLC ForConnecting Optical Fibers to Optical or Optoelectronic Devices” which isincorporated herein by reference in its entirety.

In one embodiment, the first end of the light pipe can be disposed withrespect to a multi-fiber ferrule (such as Mini-MT multi-fiber assembly)to permit light coupling into the light pipe. In one embodiment, themulti-fiber assembly can be positioned so that the optical axes of thefibers therein can be substantially aligned with the optical axis of thelight pipe or light guide. In particular, the fibers may be positioned,e.g., centered with respect to the length of transmissive material suchthat light from the fiber can be coupled into the light pipe andpropagate directly to the sloping reflective surface. In someembodiments, an anti-reflection coating or index matching can beprovided at the first end to increase coupling efficiency.

In the example embodiments shown in FIGS. 11-13, the photo-detectors 366(with a detecting surface 368), 396 (with a detecting surface 398), and425 can be surface-detecting types. The photo-detectors may includeplanar photo-sensitive surfaces oriented parallel to the surface of thedies 362, 392, 422 on which the photodetectors 366, 396, 425 aremounted. Direct coupling with such surface-detecting photo-detectorswith the second end of the light pipe can reduce signal loss. In someembodiments, the bottom surface of the coupler can be disposed withrespect to the photo-detector to couple light thereto. In certainembodiments, the bottom surface of the coupler can contact the detector,or be positioned so as to provide a gap between the bottom surface ofthe coupler and the detector. In certain embodiments, an opticallytransmissive adhesive, which in some cases may provide index matching,may exist between the bottom surface of the coupler and the detector.The detector may or may not have a glass faceplate in front of thephotosensitive surface. In some embodiments, as described below, anintermediate optical component, for example, a spacer, is disposedbetween the coupler and the photo-detector.

In one embodiment, as shown in FIGS. 11A-11C, a laser 364 can couplelight into a waveguide structure 372 having an output disposed withrespect to the second end of the light pipe, to thereby couple lightinto the second end of the light pipe. In one embodiment, the waveguidestructure 372 can be a planar waveguide formed on the planar surface ofthe die 362. In one embodiment, the planar waveguide can comprise anoptical modulator. This modulator may comprise a ring resonator or othertype of waveguide resonator or modulator such as a Mach-Zehndermodulator. Examples of different embodiments of ring resonators can befound in U.S. Pat. No. 6,895,148 titled “MODULATOR BASED ON TUNABLERESONANT CAVITY” which is incorporated herein by reference in itsentirety. Examples of different embodiments of Mach-Zehnder modulatorscan be found in U.S. Pat. No. 7,039,258 titled “DISTRIBUTED AMPLIFIEROPTICAL MODULATORS” and U.S. application Ser. No. 11/540,172 titled“DISTRIBUTED AMPLIFIER OPTICAL MODULATORS”, which are each incorporatedherein by reference in their entirety. Modulation of the light from thelaser using a modulator may be more advantageous than modulating thelaser. In one embodiment, the waveguide structure can further include anoptical waveguide grating coupler to couple light from the planarwaveguide to the second end of the light pipe. Examples of embodimentsof waveguide grating couplers are disclosed in U.S. application Ser. No.10/776,475 titled “OPTICAL WAVEGUIDE GRATING COUPLER” which isincorporated herein by reference in its entirety.

In different embodiments, the lateral spacing between the photodetector366 and the waveguide 372 is about 750 microns. In other embodiments,however, the spacing may be larger or smaller than 750 microns. Incertain embodiments, for example, the center-to-center distance is lessthan 1000 microns. In one embodiment, the center-to-center distance maybe less than 750 microns (for example, about 250 microns).

In one embodiment, a substantially optically transmissive spacer can bedisposed between the second end of the light pipe and the die so as tocouple light output from the waveguide structure into the second end ofthe light pipe. In one embodiment, the substantially opticallytransmissive spacer can include silicon having at least oneanti-reflection coating thereon. In one embodiment, the spacer can beheld in place by an optically transmissive adhesive.

In one embodiment, as shown in FIGS. 12A-12C, a laser 394 can be asurface-emitting laser. The emitting surface of the laser 394 can havean output that faces upwards, e.g., normal to the top surface of the die392, similar to the upward-facing detecting surface 398 of thephoto-detector 396, so as to couple with the second end of the lightpipe 400. Accordingly, the output surface of the laser 394 may beparallel to the top surface of the die 392 on which the laser ismounted. In one embodiment, such surface-emitting laser 394 can be aVCSEL (vertical cavity surface emitting laser). In some embodiments, thesurface emitting laser comprises a HCSEL (horizontal cavity surfaceemitting laser). Example lasers 394 comprising a stack of layers ofmaterial with an output face on the top of the stack.

In some embodiments the laser 394 and the photo-detector 396 can beseparated by 750 microns. In different embodiments, the center-to-centerdistance may be larger or smaller than 750 microns. In certainembodiments, however, the center-to-center distance is less than 1000microns. In one embodiment, the center-to-center distance may be lessthan 750 microns (for example, about 250 microns).

In one embodiment, as shown in FIGS. 13A-13C, a surface-emitting laserand a surface-detecting photo-detector can be monolithically integratedinto a single chip unit 425. As with the example configuration of FIGS.12A-12C, the emitting surface of the laser and the detecting surface ofthe photo-detector can face upward so as to couple with the second endof the light pipe 430. In one embodiment, the surface-emitting laser canbe a VCSEL or a HCSEL.

In one embodiment, the laser can be configured to emit light atapproximately 1310 nm, and the photo-detector can be configured todetect light at approximately 1490 nm. In one embodiment, the laser canbe modulated at a rate of approximately 2.5 Gbps, and the photo-detectorcan support data rate at approximately 2.5 Gbps. In one embodiment, suchmonolithically integrated chip can operate uncooled.

Based on the foregoing, one can see that there can be many possiblevariations in selection of lasers and photo-detectors, as well as howthey are positioned, oriented, integrated, and mounted. For example, asdescribed above with reference to FIGS. 3, 4A-4C, and 5A-5B, use of edgeemitting lasers and edge detectors can provide smaller footprints (forexample, an edge-emitting laser can be approximately 250 μm×250 μm) toallow implementation of more than one channel for the integratedtransceiver. In another example, described above with reference to FIGS.6A-6D, 7A-7C, and 8A-8B, use of surface-detectors can allow for morerelaxed alignment. Surface photodetectors that are commerciallyavailable can also be used. Integrating the photodetector in the die canfurther reduce package dimensions and cost while improving performanceby eliminating external electrical connections.

Aside from size and alignment considerations, optical couplingefficiency can also be considered when selecting a configuration for theintegrated transceiver. In general, when being optically coupled with acircular-cross-section waveguide (such as an optical fiber), an opticalfiber couples with a lesser efficiency to an edge detector than to asurface-photo-detector which has a larger area for receiving the lightfrom the fiber.

FIG. 15A shows an example optical coupling configuration 460 between anedge-detecting photo-diode (depicted as “PD mode”) and a circular fiber(depicted as “Fiber mode”). As shown, portions of the circle above andbelow the elliptical distribution of the PD mode do not overlap with thedetecting region of the PD, thereby reducing the optical couplingefficiency. FIG. 15B shows an exemplary relationship between suchcoupling loss between an example 5 μm single-mode fiber (SMF) separatedfrom the detecting edge of the PD by about 10 μm. The horizontal modesize of the detecting edge is held at a constant value, and the verticalmode size is varied (X-axis). As shown by line 470, the relationshipbetween coupling loss (Y-axis) and the vertical mode size (X-axis) isgenerally an inverse relationship. Based on such characterization, onecan select a desired operating configuration of an edge-detecting (oredge-emitting) component when being coupled to a fiber.

In some situations, coupling loss associated with edge-emitting lasersand edge detectors may be acceptable. In some situations, such couplingloss with for example an edge detector may not be desirable—in whichcase, surface photo-detector may be used. In some embodiments, loss andpower budget considerations may be used to select a desiredconfiguration of the integrated transceiver.

Many variations in the selections and/or orientations of lasers and/ordetectors are possible. For example, a surface emitting laser can beoriented and mounted such that the output surface faces outward(generally orthogonal to the top surface of the die) instead of theexample edge-emitting lasers (for example, in FIG. 3).

Various embodiments described herein can provide an integratedtransceiver that has a reduced form factor but that provides for highdata rates. Various features of the physical, optical, and electricaldesign may provide these and other advantages. For example, theselection, positioning, orientation, and arrangement of components asdescribed herein may result compactness, ruggedness, efficient opticalcoupling, high data rates, and ease of manufacture and repair. In someembodiments, the shape of the packaging may be useful in providing acompact and robust platform. Also, various types of electricalconnections, which may include for example pins, sockets, wires, traces,conductive pathways imbedded in ridged insulating material, or anycombination thereof, may additionally provide for a robust design thatis easy to manufacture and that uses largely existing optical andelectrical components. Other design features may contribute to theperformance and advantages provided by the designs described herein.

A wide variety of variations, however, are possible. For example,additional structural elements may be added, elements may be removed orelements may be arranged or configured differently. Similarly,processing steps may be added, removed, or ordered differently.Accordingly, although the above-disclosed embodiments have shown,described, and pointed out the novel features of the invention asapplied to the above-disclosed embodiments, it should be understood thatvarious omissions, substitutions, and changes in the form of the detailof the devices, systems, and/or methods shown may be made by thoseskilled in the art without departing from the scope of the invention.Consequently, the scope of the invention should not be limited to theforegoing description, but should be defined by the appended claims.

1. An integrated transceiver, comprising: at least one integrated circuit die including electronics thereon; a semiconductor laser disposed on said at least one integrated circuit die and in electrical communication with said electronics; a photodetector disposed on said at least one integrated circuit die and in electrical communication with said electronics; and a light pipe comprising a length of substantially optically transmissive material having a first end and a second end, said second end disposed proximal to said photodetector, said second end having a sloping reflective surface angled such that light propagating along said length from said first end to said second end is redirected to said photodetector.
 2. The transceiver of claim 1, wherein said at least one die comprises a single die.
 3. The transceiver of claim 1, wherein said electronics includes a laser driver and a transimpedence amplifier.
 4. The transceiver of claim 1, wherein said integrated circuit die comprises a semiconductor substrate or a substrate having semiconductor disposed thereon.
 5. The transceiver of claim 4, wherein said semiconductor substrate comprises a silicon substrate.
 6. The transceiver of claim 1, wherein said semiconductor laser couples light into a waveguide structure having an output disposed with respect to said second end to couple light into said second end of said light pipe.
 7. The transceiver of claim 6, wherein said waveguide structure comprises a planar waveguide.
 8. The transceiver of claim 7, wherein said planar waveguide comprises an optical modulator.
 9. The transceiver of claim 7, wherein said waveguide structure further comprises an optical waveguide grating coupler to couple into said second end of said light pipe.
 10. The transceiver of claim 6, further comprising a substantially optically transmissive spacer between said second end of said light pipe and said at least one integrated circuit die that couples light output from said waveguide structure into said second end of said light pipe.
 11. The transceiver of claim 10, wherein said substantially optically transmissive spacer comprises silicon having at least one anti-reflection coating thereon.
 12. The transceiver of claim 1, wherein said photodetector includes an optical input surface that is substantially planar.
 13. The transceiver of claim 12, wherein said at least one integrated circuit die has top and bottom surfaces and said optical input surface of said photodetector is substantially parallel to said top surface of said at least one integrated circuit die.
 14. The transceiver of claim 1, wherein said length of substantially optically transmissive material comprises glass.
 15. The transceiver of claim 1, wherein said sloping reflective surface is angled such that a difference, between an angle of said sloping reflective surface relative to said length of said light pipe and an incident angle of light with respect to a normal to said sloping reflective surface, is between about 4° and 12°.
 16. The transceiver of claim 1, wherein said sloping reflective surface comprises a total internal reflection surface.
 17. The transceiver of claim 1, wherein said first end of said light pipe is disposed with respect to a multi-fiber uniferrule to permit light coupled into said light pipe. 